so Obsrri^ations on the Nidiirul History 



cent experiments of Dr Edwards ; but that the water so absorb- 

 ed is conveyed into the aforesaid bladder is merely a conjecture ; 

 and, as appears to the authors, wholly without foundation. But 

 if we reject Townson's conjecture, what must we think of the 

 fluid with which the bladder, both in frogs and salamanders, 

 is so frequently filled ? If it come not from the kidney, from 

 what other gland or organ can it proceed ? Is it secreted by the 

 bladder itself? This supposition is not probable ; for the walls 

 of the bladder are not sufficiently furnished with vessels to se- 

 crete so great a quantity of fluid. From some experiments not 

 yet published, the authors are disposed to regard this organ as 

 a true receptacle of urine. 



9. Of tlie Organs of Sense. 



The brain of the proteus very much resembles that of the sa- 

 lamander, especially when in the larva state. The two hemis- 

 pheres are nearly cylindrical ; the lateral ventricles are large, and 

 in their posterior extremity he the corpora striata. There is al- 

 so a third ventricle, and two optic thalami, very small, and of an 

 oblong form. The carotid artery, on entering the cranium, 

 makes a twist around the aperture, and sends ofi^ the opthalmic 

 artery, which is continued, between the cranium and hemisphere, 

 to the eye : the principal trunk of this vessel then proceeds be-' 

 neath the brain, and, spreading into beautiful ramifications, is 

 distributed to the two hemispheres, &c. See Fig. 4. Plate VI. 



The eyes of this animal are situated, and we might say buried, 

 between the anterior extremity of the masseter muscles, which 

 go to be inserted in the lower jaw, and the posterior extremity 

 of the canal of the nostrils. They are inconceivably small, and 

 are placed, not in an orbit formed by bone, but in a web or 

 tissue, formed of venous and nervous ramifications. No muscle 

 nor optic nerve has yet been discovered ; but on raising the he- 

 mispheres very gently, a very subtile nerve, similar to the fine 

 thread of a spider, seemed to go to the foramen, through 

 which passed the ophthalmic artery, as seen in Fig. 4. The 

 crystalline humour is large in proportion to the other parts, 

 and has a spherical figure : the sclerotica is not white, but 

 ])lackish ; of the other parts we dare not say more ; for, from 

 their extreme minuteness, it is difficult to speak of them vv'ith 

 precisioii. 



